There exists a well known category of optical devices that perform optical filtering and can be tuned to select a narrow band of wavelengths from a wider wavelength spectrum. These devices are used in a variety of optical systems. Of specific interest are wavelength division multiplexed systems that operate typically over wavelength bands of tens of nanometers. These systems require optical performance monitoring (OPM) to ensure that signal power, signal wavelength, and signal to noise ratios (OSNR) are within specified limits. Other applications for tunable optical filters, inter alia, are for optical noise filtering, noise suppression, wavelength division demultiplexing, and optical routing.
Complex state of the art DWDM systems have many channels operating across a wide optical spectrum. To monitor these channels requires many measurements. Monitoring equipment that reduces the time and complexity of performing these measurements can significantly increase overall system performance and reduce system costs.
Other applications using wavelength selective devices in WDM systems are for selectively routing channels in large optical systems.